Don't spend rare candy on Bagon, Beldum, or Tyranitar. You can walk those in a pinch, and do some Ttar raids for more Larvitar candy.
Given that Rayquaza is a good counter for Rayquaza without outrage, I'd lean towards that, since we have about three weeks of Rayquaza and 4 days of Kyogre and Groudon. The 2078 sounds like an excellent choice, unless you have 6 Dragonites powered up to level 40 already.